1 //===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains support for writing DWARF exception info into asm files.
12 //===----------------------------------------------------------------------===//
14 #include "DwarfException.h"
15 #include "llvm/Module.h"
16 #include "llvm/CodeGen/MachineModuleInfo.h"
17 #include "llvm/CodeGen/MachineFrameInfo.h"
18 #include "llvm/CodeGen/MachineFunction.h"
19 #include "llvm/CodeGen/MachineLocation.h"
20 #include "llvm/MC/MCAsmInfo.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCExpr.h"
23 #include "llvm/MC/MCSection.h"
24 #include "llvm/MC/MCStreamer.h"
25 #include "llvm/Target/TargetData.h"
26 #include "llvm/Target/TargetFrameInfo.h"
27 #include "llvm/Target/TargetLoweringObjectFile.h"
28 #include "llvm/Target/TargetOptions.h"
29 #include "llvm/Target/TargetRegisterInfo.h"
30 #include "llvm/Support/Dwarf.h"
31 #include "llvm/Support/Mangler.h"
32 #include "llvm/Support/Timer.h"
33 #include "llvm/Support/raw_ostream.h"
34 #include "llvm/ADT/SmallString.h"
35 #include "llvm/ADT/StringExtras.h"
38 static TimerGroup &getDwarfTimerGroup() {
39 static TimerGroup DwarfTimerGroup("DWARF Exception");
40 return DwarfTimerGroup;
43 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
45 : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
46 shouldEmitTableModule(false), shouldEmitMovesModule(false),
48 if (TimePassesIsEnabled)
49 ExceptionTimer = new Timer("DWARF Exception Writer",
50 getDwarfTimerGroup());
53 DwarfException::~DwarfException() {
54 delete ExceptionTimer;
57 /// SizeOfEncodedValue - Return the size of the encoding in bytes.
58 unsigned DwarfException::SizeOfEncodedValue(unsigned Encoding) {
59 if (Encoding == dwarf::DW_EH_PE_omit)
62 switch (Encoding & 0x07) {
63 case dwarf::DW_EH_PE_absptr:
64 return TD->getPointerSize();
65 case dwarf::DW_EH_PE_udata2:
67 case dwarf::DW_EH_PE_udata4:
69 case dwarf::DW_EH_PE_udata8:
73 assert(0 && "Invalid encoded value.");
77 /// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
78 /// is shared among many Frame Description Entries. There is at least one CIE
79 /// in every non-empty .debug_frame section.
80 void DwarfException::EmitCIE(const Function *PersonalityFn, unsigned Index) {
81 // Size and sign of stack growth.
83 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
84 TargetFrameInfo::StackGrowsUp ?
85 TD->getPointerSize() : -TD->getPointerSize();
87 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
89 // Begin eh frame section.
90 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
92 if (MAI->is_EHSymbolPrivate())
93 O << MAI->getPrivateGlobalPrefix();
94 O << "EH_frame" << Index << ":\n";
96 EmitLabel("section_eh_frame", Index);
98 // Define base labels.
99 EmitLabel("eh_frame_common", Index);
101 // Define the eh frame length.
102 EmitDifference("eh_frame_common_end", Index,
103 "eh_frame_common_begin", Index, true);
104 Asm->EOL("Length of Common Information Entry");
107 EmitLabel("eh_frame_common_begin", Index);
108 Asm->EmitInt32((int)0);
109 Asm->EOL("CIE Identifier Tag");
110 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
111 Asm->EOL("CIE Version");
113 // The personality presence indicates that language specific information will
114 // show up in the eh frame. Find out how we are supposed to lower the
115 // personality function reference:
116 const MCExpr *PersonalityRef = 0;
117 bool IsPersonalityIndirect = false, IsPersonalityPCRel = false;
119 // FIXME: HANDLE STATIC CODEGEN MODEL HERE.
121 // In non-static mode, ask the object file how to represent this reference.
123 TLOF.getSymbolForDwarfGlobalReference(PersonalityFn, Asm->Mang,
125 IsPersonalityIndirect,
129 unsigned PerEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
130 if (IsPersonalityIndirect)
131 PerEncoding |= dwarf::DW_EH_PE_indirect;
132 unsigned LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
133 unsigned FDEEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
135 char Augmentation[5] = { 0 };
136 unsigned AugmentationSize = 0;
137 char *APtr = Augmentation + 1;
139 if (PersonalityRef) {
140 // There is a personality function.
142 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
145 if (UsesLSDA[Index]) {
146 // An LSDA pointer is in the FDE augmentation.
151 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
152 // A non-default pointer encoding for the FDE.
157 if (APtr != Augmentation + 1)
158 Augmentation[0] = 'z';
160 Asm->EmitString(Augmentation);
161 Asm->EOL("CIE Augmentation");
164 Asm->EmitULEB128Bytes(1);
165 Asm->EOL("CIE Code Alignment Factor");
166 Asm->EmitSLEB128Bytes(stackGrowth);
167 Asm->EOL("CIE Data Alignment Factor");
168 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
169 Asm->EOL("CIE Return Address Column");
171 Asm->EmitULEB128Bytes(AugmentationSize);
172 Asm->EOL("Augmentation Size");
174 Asm->EmitInt8(PerEncoding);
175 Asm->EOL("Personality", PerEncoding);
177 // If there is a personality, we need to indicate the function's location.
178 if (PersonalityRef) {
179 // If the reference to the personality function symbol is not already
180 // pc-relative, then we need to subtract our current address from it. Do
181 // this by emitting a label and subtracting it from the expression we
182 // already have. This is equivalent to emitting "foo - .", but we have to
183 // emit the label for "." directly.
184 if (!IsPersonalityPCRel) {
185 SmallString<64> Name;
186 raw_svector_ostream(Name) << MAI->getPrivateGlobalPrefix()
187 << "personalityref_addr" << Asm->getFunctionNumber() << "_" << Index;
188 MCSymbol *DotSym = Asm->OutContext.GetOrCreateSymbol(Name.str());
189 Asm->OutStreamer.EmitLabel(DotSym);
192 MCBinaryExpr::CreateSub(PersonalityRef,
193 MCSymbolRefExpr::Create(DotSym,Asm->OutContext),
197 O << MAI->getData32bitsDirective();
198 PersonalityRef->print(O, MAI);
199 Asm->EOL("Personality");
201 Asm->EmitInt8(LSDAEncoding);
202 Asm->EOL("LSDA Encoding", LSDAEncoding);
204 Asm->EmitInt8(FDEEncoding);
205 Asm->EOL("FDE Encoding", FDEEncoding);
208 // Indicate locations of general callee saved registers in frame.
209 std::vector<MachineMove> Moves;
210 RI->getInitialFrameState(Moves);
211 EmitFrameMoves(NULL, 0, Moves, true);
213 // On Darwin the linker honors the alignment of eh_frame, which means it must
214 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
215 // holes which confuse readers of eh_frame.
216 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
217 EmitLabel("eh_frame_common_end", Index);
222 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
223 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
224 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
225 "Should not emit 'available externally' functions at all");
227 const Function *TheFunc = EHFrameInfo.function;
229 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
231 // Externally visible entry into the functions eh frame info. If the
232 // corresponding function is static, this should not be externally visible.
233 if (!TheFunc->hasLocalLinkage())
234 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
235 O << GlobalEHDirective << EHFrameInfo.FnName << '\n';
237 // If corresponding function is weak definition, this should be too.
238 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
239 O << MAI->getWeakDefDirective() << EHFrameInfo.FnName << '\n';
241 // If corresponding function is hidden, this should be too.
242 if (TheFunc->hasHiddenVisibility())
243 if (const char *HiddenDirective = MAI->getHiddenDirective())
244 O << HiddenDirective << EHFrameInfo.FnName << '\n' ;
246 // If there are no calls then you can't unwind. This may mean we can omit the
247 // EH Frame, but some environments do not handle weak absolute symbols. If
248 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
249 // info is to be available for non-EH uses.
250 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
251 (!TheFunc->isWeakForLinker() ||
252 !MAI->getWeakDefDirective() ||
253 MAI->getSupportsWeakOmittedEHFrame())) {
254 O << EHFrameInfo.FnName << " = 0\n";
255 // This name has no connection to the function, so it might get
256 // dead-stripped when the function is not, erroneously. Prohibit
257 // dead-stripping unconditionally.
258 if (const char *UsedDirective = MAI->getUsedDirective())
259 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
261 O << EHFrameInfo.FnName << ":\n";
264 EmitDifference("eh_frame_end", EHFrameInfo.Number,
265 "eh_frame_begin", EHFrameInfo.Number, true);
266 Asm->EOL("Length of Frame Information Entry");
268 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
270 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
271 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
274 Asm->EOL("FDE CIE offset");
276 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
277 Asm->EOL("FDE initial location");
278 EmitDifference("eh_func_end", EHFrameInfo.Number,
279 "eh_func_begin", EHFrameInfo.Number, true);
280 Asm->EOL("FDE address range");
282 // If there is a personality and landing pads then point to the language
283 // specific data area in the exception table.
284 if (MMI->getPersonalities()[0] != NULL) {
285 bool is4Byte = TD->getPointerSize() == sizeof(int32_t);
287 Asm->EmitULEB128Bytes(is4Byte ? 4 : 8);
288 Asm->EOL("Augmentation size");
290 if (EHFrameInfo.hasLandingPads)
291 EmitReference("exception", EHFrameInfo.Number, true, false);
294 Asm->EmitInt32((int)0);
296 Asm->EmitInt64((int)0);
298 Asm->EOL("Language Specific Data Area");
300 Asm->EmitULEB128Bytes(0);
301 Asm->EOL("Augmentation size");
304 // Indicate locations of function specific callee saved registers in frame.
305 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
308 // On Darwin the linker honors the alignment of eh_frame, which means it
309 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
310 // get holes which confuse readers of eh_frame.
311 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
313 EmitLabel("eh_frame_end", EHFrameInfo.Number);
315 // If the function is marked used, this table should be also. We cannot
316 // make the mark unconditional in this case, since retaining the table also
317 // retains the function in this case, and there is code around that depends
318 // on unused functions (calling undefined externals) being dead-stripped to
319 // link correctly. Yes, there really is.
320 if (MMI->isUsedFunction(EHFrameInfo.function))
321 if (const char *UsedDirective = MAI->getUsedDirective())
322 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
328 /// SharedTypeIds - How many leading type ids two landing pads have in common.
329 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
330 const LandingPadInfo *R) {
331 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
332 unsigned LSize = LIds.size(), RSize = RIds.size();
333 unsigned MinSize = LSize < RSize ? LSize : RSize;
336 for (; Count != MinSize; ++Count)
337 if (LIds[Count] != RIds[Count])
343 /// PadLT - Order landing pads lexicographically by type id.
344 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
345 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
346 unsigned LSize = LIds.size(), RSize = RIds.size();
347 unsigned MinSize = LSize < RSize ? LSize : RSize;
349 for (unsigned i = 0; i != MinSize; ++i)
350 if (LIds[i] != RIds[i])
351 return LIds[i] < RIds[i];
353 return LSize < RSize;
356 /// ComputeActionsTable - Compute the actions table and gather the first action
357 /// index for each landing pad site.
358 unsigned DwarfException::
359 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
360 SmallVectorImpl<ActionEntry> &Actions,
361 SmallVectorImpl<unsigned> &FirstActions) {
363 // The action table follows the call-site table in the LSDA. The individual
364 // records are of two types:
367 // * Exception specification
369 // The two record kinds have the same format, with only small differences.
370 // They are distinguished by the "switch value" field: Catch clauses
371 // (TypeInfos) have strictly positive switch values, and exception
372 // specifications (FilterIds) have strictly negative switch values. Value 0
373 // indicates a catch-all clause.
375 // Negative type IDs index into FilterIds. Positive type IDs index into
376 // TypeInfos. The value written for a positive type ID is just the type ID
377 // itself. For a negative type ID, however, the value written is the
378 // (negative) byte offset of the corresponding FilterIds entry. The byte
379 // offset is usually equal to the type ID (because the FilterIds entries are
380 // written using a variable width encoding, which outputs one byte per entry
381 // as long as the value written is not too large) but can differ. This kind
382 // of complication does not occur for positive type IDs because type infos are
383 // output using a fixed width encoding. FilterOffsets[i] holds the byte
384 // offset corresponding to FilterIds[i].
386 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
387 SmallVector<int, 16> FilterOffsets;
388 FilterOffsets.reserve(FilterIds.size());
391 for (std::vector<unsigned>::const_iterator
392 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
393 FilterOffsets.push_back(Offset);
394 Offset -= MCAsmInfo::getULEB128Size(*I);
397 FirstActions.reserve(LandingPads.size());
400 unsigned SizeActions = 0;
401 const LandingPadInfo *PrevLPI = 0;
403 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
404 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
405 const LandingPadInfo *LPI = *I;
406 const std::vector<int> &TypeIds = LPI->TypeIds;
407 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
408 unsigned SizeSiteActions = 0;
410 if (NumShared < TypeIds.size()) {
411 unsigned SizeAction = 0;
412 ActionEntry *PrevAction = 0;
415 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
416 assert(Actions.size());
417 PrevAction = &Actions.back();
418 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
419 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
421 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
423 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
424 SizeAction += -PrevAction->NextAction;
425 PrevAction = PrevAction->Previous;
429 // Compute the actions.
430 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
431 int TypeID = TypeIds[J];
432 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
433 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
434 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
436 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
437 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
438 SizeSiteActions += SizeAction;
440 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
441 Actions.push_back(Action);
442 PrevAction = &Actions.back();
445 // Record the first action of the landing pad site.
446 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
447 } // else identical - re-use previous FirstAction
449 // Information used when created the call-site table. The action record
450 // field of the call site record is the offset of the first associated
451 // action record, relative to the start of the actions table. This value is
452 // biased by 1 (1 in dicating the start of the actions table), and 0
453 // indicates that there are no actions.
454 FirstActions.push_back(FirstAction);
456 // Compute this sites contribution to size.
457 SizeActions += SizeSiteActions;
465 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
466 /// has a try-range containing the call, a non-zero landing pad, and an
467 /// appropriate action. The entry for an ordinary call has a try-range
468 /// containing the call and zero for the landing pad and the action. Calls
469 /// marked 'nounwind' have no entry and must not be contained in the try-range
470 /// of any entry - they form gaps in the table. Entries must be ordered by
471 /// try-range address.
472 void DwarfException::
473 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
474 const RangeMapType &PadMap,
475 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
476 const SmallVectorImpl<unsigned> &FirstActions) {
477 // The end label of the previous invoke or nounwind try-range.
478 unsigned LastLabel = 0;
480 // Whether there is a potentially throwing instruction (currently this means
481 // an ordinary call) between the end of the previous try-range and now.
482 bool SawPotentiallyThrowing = false;
484 // Whether the last CallSite entry was for an invoke.
485 bool PreviousIsInvoke = false;
487 // Visit all instructions in order of address.
488 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
490 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
492 if (!MI->isLabel()) {
493 if (MI->getDesc().isCall()) {
494 // Don't mark a call as potentially throwing if the function it's
495 // calling is marked "nounwind".
496 bool DoesNotThrow = false;
497 bool SawFunc = false;
498 for (unsigned OI = 0, OE = MI->getNumOperands(); OI != OE; ++OI) {
499 const MachineOperand &MO = MI->getOperand(OI);
502 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
504 // Be conservative. If we have more than one function operand
505 // for this call, then we can't make the assumption that it's
506 // the callee and not a parameter to the call.
508 // FIXME: Determine if there's a way to say that `F' is the
509 // callee or parameter.
510 DoesNotThrow = false;
513 if (F->doesNotThrow()) {
522 SawPotentiallyThrowing = true;
528 unsigned BeginLabel = MI->getOperand(0).getImm();
529 assert(BeginLabel && "Invalid label!");
531 // End of the previous try-range?
532 if (BeginLabel == LastLabel)
533 SawPotentiallyThrowing = false;
535 // Beginning of a new try-range?
536 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
537 if (L == PadMap.end())
538 // Nope, it was just some random label.
541 const PadRange &P = L->second;
542 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
543 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
544 "Inconsistent landing pad map!");
546 // For Dwarf exception handling (SjLj handling doesn't use this). If some
547 // instruction between the previous try-range and this one may throw,
548 // create a call-site entry with no landing pad for the region between the
550 if (SawPotentiallyThrowing &&
551 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
552 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
553 CallSites.push_back(Site);
554 PreviousIsInvoke = false;
557 LastLabel = LandingPad->EndLabels[P.RangeIndex];
558 assert(BeginLabel && LastLabel && "Invalid landing pad!");
560 if (LandingPad->LandingPadLabel) {
561 // This try-range is for an invoke.
562 CallSiteEntry Site = {
565 LandingPad->LandingPadLabel,
566 FirstActions[P.PadIndex]
569 // Try to merge with the previous call-site. SJLJ doesn't do this
570 if (PreviousIsInvoke &&
571 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
572 CallSiteEntry &Prev = CallSites.back();
573 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
574 // Extend the range of the previous entry.
575 Prev.EndLabel = Site.EndLabel;
580 // Otherwise, create a new call-site.
581 CallSites.push_back(Site);
582 PreviousIsInvoke = true;
585 PreviousIsInvoke = false;
590 // If some instruction between the previous try-range and the end of the
591 // function may throw, create a call-site entry with no landing pad for the
592 // region following the try-range.
593 if (SawPotentiallyThrowing &&
594 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
595 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
596 CallSites.push_back(Site);
600 /// EmitExceptionTable - Emit landing pads and actions.
602 /// The general organization of the table is complex, but the basic concepts are
603 /// easy. First there is a header which describes the location and organization
604 /// of the three components that follow.
606 /// 1. The landing pad site information describes the range of code covered by
607 /// the try. In our case it's an accumulation of the ranges covered by the
608 /// invokes in the try. There is also a reference to the landing pad that
609 /// handles the exception once processed. Finally an index into the actions
611 /// 2. The action table, in our case, is composed of pairs of type IDs and next
612 /// action offset. Starting with the action index from the landing pad
613 /// site, each type ID is checked for a match to the current exception. If
614 /// it matches then the exception and type id are passed on to the landing
615 /// pad. Otherwise the next action is looked up. This chain is terminated
616 /// with a next action of zero. If no type id is found then the frame is
617 /// unwound and handling continues.
618 /// 3. Type ID table contains references to all the C++ typeinfo for all
619 /// catches in the function. This tables is reverse indexed base 1.
620 void DwarfException::EmitExceptionTable() {
621 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
622 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
623 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
624 if (PadInfos.empty()) return;
626 // Sort the landing pads in order of their type ids. This is used to fold
627 // duplicate actions.
628 SmallVector<const LandingPadInfo *, 64> LandingPads;
629 LandingPads.reserve(PadInfos.size());
631 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
632 LandingPads.push_back(&PadInfos[i]);
634 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
636 // Compute the actions table and gather the first action index for each
638 SmallVector<ActionEntry, 32> Actions;
639 SmallVector<unsigned, 64> FirstActions;
640 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions,
643 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
644 // by try-range labels when lowered). Ordinary calls do not, so appropriate
645 // try-ranges for them need be deduced when using DWARF exception handling.
647 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
648 const LandingPadInfo *LandingPad = LandingPads[i];
649 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
650 unsigned BeginLabel = LandingPad->BeginLabels[j];
651 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
652 PadRange P = { i, j };
653 PadMap[BeginLabel] = P;
657 // Compute the call-site table.
658 SmallVector<CallSiteEntry, 64> CallSites;
659 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
664 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
665 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
666 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
667 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
668 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
674 SizeSites = CallSites.size() *
675 (SiteStartSize + SiteLengthSize + LandingPadSize);
677 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
678 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
680 SizeSites += MCAsmInfo::getULEB128Size(i);
684 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
685 unsigned TTypeFormat;
686 unsigned TypeFormatSize;
689 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
690 // that we're omitting that bit.
691 TTypeFormat = dwarf::DW_EH_PE_omit;
692 TypeFormatSize = SizeOfEncodedValue(dwarf::DW_EH_PE_absptr);
694 // Okay, we have actual filters or typeinfos to emit. As such, we need to
695 // pick a type encoding for them. We're about to emit a list of pointers to
696 // typeinfo objects at the end of the LSDA. However, unless we're in static
697 // mode, this reference will require a relocation by the dynamic linker.
699 // Because of this, we have a couple of options:
701 // 1) If we are in -static mode, we can always use an absolute reference
702 // from the LSDA, because the static linker will resolve it.
704 // 2) Otherwise, if the LSDA section is writable, we can output the direct
705 // reference to the typeinfo and allow the dynamic linker to relocate
706 // it. Since it is in a writable section, the dynamic linker won't
709 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
710 // we need to use some form of indirection. For example, on Darwin,
711 // we can output a statically-relocatable reference to a dyld stub. The
712 // offset to the stub is constant, but the contents are in a section
713 // that is updated by the dynamic linker. This is easy enough, but we
714 // need to tell the personality function of the unwinder to indirect
715 // through the dyld stub.
717 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
718 // somewhere. This predicate should be moved to a shared location that is
719 // in target-independent code.
721 if (LSDASection->getKind().isWriteable() ||
722 Asm->TM.getRelocationModel() == Reloc::Static)
723 TTypeFormat = dwarf::DW_EH_PE_absptr;
725 TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
726 dwarf::DW_EH_PE_sdata4;
728 TypeFormatSize = SizeOfEncodedValue(TTypeFormat);
731 // Begin the exception table.
732 Asm->OutStreamer.SwitchSection(LSDASection);
733 Asm->EmitAlignment(2, 0, 0, false);
735 O << "GCC_except_table" << SubprogramCount << ":\n";
737 // The type infos need to be aligned. GCC does this by inserting padding just
738 // before the type infos. However, this changes the size of the exception
739 // table, so you need to take this into account when you output the exception
740 // table size. However, the size is output using a variable length encoding.
741 // So by increasing the size by inserting padding, you may increase the number
742 // of bytes used for writing the size. If it increases, say by one byte, then
743 // you now need to output one less byte of padding to get the type infos
744 // aligned. However this decreases the size of the exception table. This
745 // changes the value you have to output for the exception table size. Due to
746 // the variable length encoding, the number of bytes used for writing the
747 // length may decrease. If so, you then have to increase the amount of
748 // padding. And so on. If you look carefully at the GCC code you will see that
749 // it indeed does this in a loop, going on and on until the values stabilize.
750 // We chose another solution: don't output padding inside the table like GCC
751 // does, instead output it before the table.
752 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
753 unsigned TyOffset = sizeof(int8_t) + // Call site format
754 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
755 SizeSites + SizeActions + SizeTypes;
756 unsigned TotalSize = sizeof(int8_t) + // LPStart format
757 sizeof(int8_t) + // TType format
759 MCAsmInfo::getULEB128Size(TyOffset) : 0) + // TType base offset
761 unsigned SizeAlign = (4 - TotalSize) & 3;
763 for (unsigned i = 0; i != SizeAlign; ++i) {
768 EmitLabel("exception", SubprogramCount);
771 SmallString<16> LSDAName;
772 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
773 "_LSDA_" << Asm->getFunctionNumber();
774 O << LSDAName.str() << ":\n";
778 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
779 Asm->EOL("@LPStart format", dwarf::DW_EH_PE_omit);
781 Asm->EmitInt8(TTypeFormat);
782 Asm->EOL("@TType format", TTypeFormat);
785 Asm->EmitULEB128Bytes(TyOffset);
786 Asm->EOL("@TType base offset");
789 // SjLj Exception handling
791 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
792 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
793 Asm->EmitULEB128Bytes(SizeSites);
794 Asm->EOL("Call site table length");
796 // Emit the landing pad site information.
798 for (SmallVectorImpl<CallSiteEntry>::const_iterator
799 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
800 const CallSiteEntry &S = *I;
802 // Offset of the landing pad, counted in 16-byte bundles relative to the
804 Asm->EmitULEB128Bytes(idx);
805 Asm->EOL("Landing pad");
807 // Offset of the first associated action record, relative to the start of
808 // the action table. This value is biased by 1 (1 indicates the start of
809 // the action table), and 0 indicates that there are no actions.
810 Asm->EmitULEB128Bytes(S.Action);
814 // DWARF Exception handling
815 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
817 // The call-site table is a list of all call sites that may throw an
818 // exception (including C++ 'throw' statements) in the procedure
819 // fragment. It immediately follows the LSDA header. Each entry indicates,
820 // for a given call, the first corresponding action record and corresponding
823 // The table begins with the number of bytes, stored as an LEB128
824 // compressed, unsigned integer. The records immediately follow the record
825 // count. They are sorted in increasing call-site address. Each record
828 // * The position of the call-site.
829 // * The position of the landing pad.
830 // * The first action record for that call site.
832 // A missing entry in the call-site table indicates that a call is not
833 // supposed to throw.
835 // Emit the landing pad call site table.
836 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
837 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
838 Asm->EmitULEB128Bytes(SizeSites);
839 Asm->EOL("Call site table size");
841 for (SmallVectorImpl<CallSiteEntry>::const_iterator
842 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
843 const CallSiteEntry &S = *I;
844 const char *BeginTag;
845 unsigned BeginNumber;
848 BeginTag = "eh_func_begin";
849 BeginNumber = SubprogramCount;
852 BeginNumber = S.BeginLabel;
855 // Offset of the call site relative to the previous call site, counted in
856 // number of 16-byte bundles. The first call site is counted relative to
857 // the start of the procedure fragment.
858 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
860 Asm->EOL("Region start");
863 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
866 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
868 Asm->EOL("Region length");
870 // Offset of the landing pad, counted in 16-byte bundles relative to the
875 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
878 Asm->EOL("Landing pad");
880 // Offset of the first associated action record, relative to the start of
881 // the action table. This value is biased by 1 (1 indicates the start of
882 // the action table), and 0 indicates that there are no actions.
883 Asm->EmitULEB128Bytes(S.Action);
888 // Emit the Action Table.
889 for (SmallVectorImpl<ActionEntry>::const_iterator
890 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
891 const ActionEntry &Action = *I;
895 // Used by the runtime to match the type of the thrown exception to the
896 // type of the catch clauses or the types in the exception specification.
898 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
899 Asm->EOL("TypeInfo index");
903 // Self-relative signed displacement in bytes of the next action record,
904 // or 0 if there is no next action record.
906 Asm->EmitSLEB128Bytes(Action.NextAction);
907 Asm->EOL("Next action");
910 // Emit the Catch TypeInfos.
911 for (std::vector<GlobalVariable *>::const_reverse_iterator
912 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
913 const GlobalVariable *GV = *I;
917 O << Asm->Mang->getMangledName(GV);
922 Asm->EOL("TypeInfo");
925 // Emit the Exception Specifications.
926 for (std::vector<unsigned>::const_iterator
927 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
928 unsigned TypeID = *I;
929 Asm->EmitULEB128Bytes(TypeID);
931 Asm->EOL("Exception specification");
936 Asm->EmitAlignment(2, 0, 0, false);
939 /// EndModule - Emit all exception information that should come after the
941 void DwarfException::EndModule() {
942 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
945 if (!shouldEmitMovesModule && !shouldEmitTableModule)
948 if (TimePassesIsEnabled)
949 ExceptionTimer->startTimer();
951 const std::vector<Function *> Personalities = MMI->getPersonalities();
953 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
954 EmitCIE(Personalities[I], I);
956 for (std::vector<FunctionEHFrameInfo>::iterator
957 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
960 if (TimePassesIsEnabled)
961 ExceptionTimer->stopTimer();
964 /// BeginFunction - Gather pre-function exception information. Assumes it's
965 /// being emitted immediately after the function entry point.
966 void DwarfException::BeginFunction(MachineFunction *MF) {
967 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
969 if (TimePassesIsEnabled)
970 ExceptionTimer->startTimer();
973 shouldEmitTable = shouldEmitMoves = false;
975 // Map all labels and get rid of any dead landing pads.
976 MMI->TidyLandingPads();
978 // If any landing pads survive, we need an EH table.
979 if (!MMI->getLandingPads().empty())
980 shouldEmitTable = true;
982 // See if we need frame move info.
983 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
984 shouldEmitMoves = true;
986 if (shouldEmitMoves || shouldEmitTable)
987 // Assumes in correct section after the entry point.
988 EmitLabel("eh_func_begin", ++SubprogramCount);
990 shouldEmitTableModule |= shouldEmitTable;
991 shouldEmitMovesModule |= shouldEmitMoves;
993 if (TimePassesIsEnabled)
994 ExceptionTimer->stopTimer();
997 /// EndFunction - Gather and emit post-function exception information.
999 void DwarfException::EndFunction() {
1000 if (!shouldEmitMoves && !shouldEmitTable) return;
1002 if (TimePassesIsEnabled)
1003 ExceptionTimer->startTimer();
1005 EmitLabel("eh_func_end", SubprogramCount);
1006 EmitExceptionTable();
1008 std::string FunctionEHName =
1009 Asm->Mang->getMangledName(MF->getFunction(), ".eh",
1010 Asm->MAI->is_EHSymbolPrivate());
1012 // Save EH frame information
1013 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHName, SubprogramCount,
1014 MMI->getPersonalityIndex(),
1015 MF->getFrameInfo()->hasCalls(),
1016 !MMI->getLandingPads().empty(),
1017 MMI->getFrameMoves(),
1018 MF->getFunction()));
1020 // Record if this personality index uses a landing pad.
1021 UsesLSDA[MMI->getPersonalityIndex()] |= !MMI->getLandingPads().empty();
1023 if (TimePassesIsEnabled)
1024 ExceptionTimer->stopTimer();